Glossary

Bidirectional reflectance distribution function

“The bidirectional reflectance distribution function (BRDF) is a function of four real variables that defines how light is reflected at an opaque surface. It is employed in the optics of real-world light, in computer graphics algorithms, and in computer vision algorithms.”

~ Wikipedia on BRDF

A BRDF model is a 7 dimensional model containing geometry, textures and reflectance of the subject.

The seven dimensions of the BRDF are as follows:

• 3 cartesian X,Y,Z
• 2 for the entry angle
• 2 for the exit angle of the light.

---

Covert modeling

Covert modeling refers to both covertly modeling aspects of a subject i.e. without express consent.

Main known cases are

• Covertly modeling the human appearance into 7-dimensional [[#Bidirectional reflectance distribution function|]] model or other type of model.
• Covertly modeling the human voice

There is work ongoing to model e.g. human's style of writing, but this is probably not as drastic a threat as the covert modeling of appearance and of voice.

---

Light stage

The ESPER LightCage - 3D face scanning rig is a modern light stage

“A light stage or light cage is equipment used for shape, texture, reflectance and motion capture often with structured light and a multi-camera setup.”

~ Wikipedia on light stages